What is Cosmology: Definition and 925 Discussions

Cosmology (from Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is a branch of astronomy concerned with the studies of the origin and evolution of the universe, from the Big Bang to today and on into the future. It is the scientific study of the origin, evolution, and eventual fate of the universe. Physical cosmology is the scientific study of the universe's origin, its large-scale structures and dynamics, and its ultimate fate, as well as the laws of science that govern these areas.The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, and in 1731 taken up in Latin by German philosopher Christian Wolff, in Cosmologia Generalis.Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology.
Physical cosmology is studied by scientists, such as astronomers and physicists, as well as philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Because of this shared scope with philosophy, theories in physical cosmology may include both scientific and non-scientific propositions, and may depend upon assumptions that cannot be tested. Cosmology differs from astronomy in that the former is concerned with the Universe as a whole while the latter deals with individual celestial objects. Modern physical cosmology is dominated by the Big Bang theory, which attempts to bring together observational astronomy and particle physics; more specifically, a standard parameterization of the Big Bang with dark matter and dark energy, known as the Lambda-CDM model.
Theoretical astrophysicist David N. Spergel has described cosmology as a "historical science" because "when we look out in space, we look back in time" due to the finite nature of the speed of light.

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  1. E

    Can information be transmitted faster than c in inflationary cosmology?

    can information be transmitted faster than c in inflationary cosmology where with a large positive cosmological constant, space is itself expanding in an exponential faster than c manner?
  2. marcus

    Path Integral formulation of Loop Cosmology (a first)

    Today (17 March) we got our first news of a Path Integral formulation of LQC. Adam Henderson is a PhD student in Ashtekar's group at Penn State. He gave an internationally distributed seminar talk on his research. http://relativity.phys.lsu.edu/ilqgs/henderson031709.pdf...
  3. I

    Exploring Cosmology with Balloons and Foam: A New Perspective

    Hi, to pick up on marcus' https://www.physicsforums.com/showpost.php?p=2015482&postcount=67" in the sticky thread: Recently, I tried to see where this analogy could bring us if evaluated properly, and I was surprised to find that it is actually far better than what marcus pessimistically...
  4. marcus

    Tests of LQG in cosmology (proposals, prospects etc)

    In the last couple of years there'v been several papers on this, often by people I hadn't heard of before. The question came up in another thread "can you summarize in a single post" the various ideas being discussed? Personally I couldn't but I can dig up some links. Toss them out for you to...
  5. Dadface

    Does cosmology have the answers?

    Armed with a mass of observations and mathematical equations cosmologists tell us that the universe started with a big bang and that its ultimate fate is,as yet,unknown.Fair enough but now the ordinary person in the street is starting to believe the big bang theory and that we will soon have a...
  6. Fredrik

    Definitions (continued from the cosmology forum)

    This is a reply to a comment made in the cosmology forum. That's not correct. Do you really believe that physicists are that dumb? The real story goes something like this: The speed of light is a constant in the real world. Therefore, we define a mathematical model in which the speed of...
  7. wolram

    Cosmology: Futility of Exploring Beyond Our Solar System

    Since the speed of light has been proven to be an absolute limit on the speed of travel, it is obvious humans will never reach beyond our solar system, humans may do some fantastic parallax measurements, but beyond them we will never have any thing other than a rubber ruler to measure with...
  8. wolram

    Critique of relativistic cosmology

    arXiv:0901.1956 [ps, pdf, other] Title: A Critique of the relativistic cosmology Authors: R. K. Thakur Comments: 8 pages, Comments welcome Subjects: General Physics (physics.gen-ph)
  9. P

    Cosmology Question that I really don't have a clue on.

    Homework Statement a) Using the Robertson-Walker metric, write down an expression for the proper distance in terms of the coordinate r. For objects moving with the expansion of the universe, show that the proper distance increases with time in the manner described by the Hubble Law. b) Use...
  10. turbo

    SDSS Quasars & Cosmology: Challenges to Current Models

    SDSS is perhaps the most ambitious astronomical survey ever undertaken, and it has provided a wealth of new data. Unfortunately for cosmologists (or fortunately, if cosmologists are willing to re-group), some of the findings are quite inconsistent with their expectations. Scroll down to Nov 2...
  11. marcus

    Tighter bounds on cosmo parameters (Chandra Cluster Cosmology Project)

    http://arxiv.org/abs/0812.2720 Chandra Cluster Cosmology Project III: Cosmological Parameter Constraints A.Vikhlinin, A.V.Kravtsov, R.A.Burenin, H.Ebeling, W.R.Forman, A.Hornstrup, C.Jones, S.S.Murray, D.Nagai, H.Quintana, A.Voevodkin ApJ, in press: Feb 10, 2009 issue (Submitted on 15 Dec...
  12. marcus

    Ways to accommodate modern cosmology

    People find their own ways of making sense of modern cosmology. Unless they are utterly unable to get comfortable and reject it whole hog (as some do quite vehemently :biggrin:). If you have a way of making your peace with cosmology, feel free to describe how you do it. Or try this recipe and...
  13. R

    I Deciding Cosmology or Astrophysics?

    First i need someone to help break it down what's the difference. Instead of just saying the origins of space is cosmos. Ima tell you what I am interested in and let me know which one i will do better in. I am interested in learning about space and how it was created, not only I am interested in...
  14. wolram

    Six puzzles for LCDM cosmology

    [37] arXiv:0811.4684 [ps, pdf, other] Title: Six Puzzles for LCDM Cosmology Authors: L. Perivolaropoulos Comments: 9 pages, 3 figures. Invited article to the TSPU anniversary volume "The Problems of Modern Cosmology" on the occasion of the 50th birthday of Prof. S. D. Odintsov Subjects...
  15. M

    Cosmology Paper Ideas: Need Help!

    I have to write a 4000 word paper for my Astronomy 302 (Foundations of Cosmology) class and I really do not know what to do. I was thinking about doing it on the effects black holes on the furture of the universe but I can not find any scholarly peer-reviewed journal articles on it to write a...
  16. G

    Cosmology, K=0, Matter dominated, energy density

    Homework Statement For K=0 of matter dominated universe, i.e at z>>1, find the energy density of starlight if f portion of matter condensed in solar type stars and the stars are uniformly distributed in space. Homework Equations Friedman eqn: \rho_m = \frac{3H^2}{8 \pi G} The...
  17. T

    Comments about an issue in cosmology?

    Learned Gentlemen, My Doctorate is in Medicine, so my questions and comments might be below you. Where can I ask questions and make comments about an issue in cosmology? Thanks, tfb
  18. F

    Cosmology and Energy Quantization in Matter

    Quantum Wave Cosmology is a niche in cosmology that consists of a group of “not easily refuted” protoscience ideas about a universe composed of nothing but energy. A few QWC ideas include: The universe is composed of one commodity, energy. Energy cannot be created or destroyed and so...
  19. wolram

    ICosmo: an Interactive Cosmology Package

    arXiv:0810.1285 [ps, pdf, other] Title: iCosmo: an Interactive Cosmology Package Authors: Alexandre Refregier (1), Adam Amara (2), Thomas Kitching (3), Anais Rassat (1) ((1) CEA Saclay, (2) ETH Zurich, (3) Univ. Oxford) Comments: 5 Latex pages including 2 tables and 4 figures. Submitted to...
  20. wolram

    Practical cosmology and cosmology physics

    arXiv:0809.1084 [pdf] Title: Practical cosmology and cosmological physics Authors: Yu. Baryshev (1), I. Taganov (2), P. Teerikorpi (3) ((1)Astron. Inst. St.-Petersburg Univ., (2)Russ. Geograph. Soc., (3)Tuorla Obs. Turku Univ.) Comments: 16 pages, summary of the conference "Problems...
  21. WCOLtd

    3 questions on Physical Cosmology

    First question: According to Hubble's Law, the redshift observed by distant galaxies are proportional to their distance. This is what I already know: It says on wikipedia that Hubble observed cepheid variable stars in a spiral nebulae to calculate their distance, cepheid variable stars are...
  22. 8

    Finding Cosmology Resources for Beginners

    I would appreciate some guidance. I don't get very far in reading peer-reviewed papers before I'm really confused --- they're way beyond my level. Even some posts on this forum are a little beyond me. And "popular" books can be misleading or just plain wrong ---and there are LOTS of...
  23. marcus

    Observing Quasar Accretion Disks: Scientists See Standard Cosmology at Work

    Nice picture of quasar accretion disk---pat on back for standard cosmology in Nature The 24 July issue of Nature reports some beautiful observational work, using a polarized light filter. Actually able to SEE the hot blue accretion disk whirling around a supermassive black hole at the center of...
  24. marcus

    The physical meaning of expansion in cosmology

    The aim of the thread is to offer a non-technical concrete way of understanding the standard model. Usual metric, equations, parameters are in the background but the focus here is on unmathematical presentation, indicating how key physical quantities could (ideally!) be measured. When I talk...
  25. S

    Suggest good articles on Loop Quantum Cosmology

    please suggest good articles on Loop Quantum Cosmology If you have links of good articles and review papers of Loop Quantum Cosmology please post here
  26. Y

    Entropy & Cosmology: Arrow of Time Paradox

    The question of the "arrow of time" and increasing entropy is not as clean cut as one might imagine. I think it it R.Penrose that pointed out that while a simple application of thermodymanis predicts the "heat death" of the universe where everything is cold and in thermal equilibrium, there is...
  27. N

    Cosmology: Equation of state parameter

    Homework Statement Hi all. The pressure in a multi-component universe is additive, just as the energy-density is: P = \sum\limits_i {w_i \varepsilon _i } \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{and}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\varepsilon = \sum\limits_i {\varepsilon _i } But...
  28. H

    Does the accelerated Expansion add credibility to Steady State Cosmology?

    Recently the expansion of the Universe has been found to accelerate. When studying Hoyle, Gold and Bondi's Steady State Cosmology, it clearly predicts an acceleration like this. I realize that this theory has been 'put to bed', and abolished, and all the other colorful language people like to...
  29. marcus

    Video lecture on Loop Quantum Cosmology

    LQC is the dominant approach to quantum cosmology these days, if you gauge by recent peer-review publication and citations in the professional literature. So anybody who wants to know about quantum cosmology could be well advised to get an introduction to LQC. Parampreet Singh is one of the...
  30. N

    What Does the Maximum Proper Distance at z ~ 1.7 Mean in Cosmology?

    Homework Statement Hi all. When looking at a graph that shows the proper distance at the time of emission as a function of the redshift z in a model-universe with only matter, the proper distance at time of emission has a maximum at about z ~ 1.7. What does this maximum mean? I can see...
  31. A

    Learn Cosmology: Books for Self-Learning Up to Grad Level

    I have long been interested in cosmology, and I took a course with the same title in undergrad. We used Liddle's book An Introduction to Modern Cosmology which I thought was pretty good, but it was relatively short. I have knowledge of mathematics and physics up to early graduate level (got my...
  32. N

    Astrophysics homework: Cosmology

    [SOLVED] Astrophysics homework: Cosmology Homework Statement I have to show that during the Big Bang Nuchleosynthesis, the scalefactor is approximately given by a(t) = \left( {4H_0^2 \Omega _{r,0} } \right)^{1/4} \sqrt t The Attempt at a Solution Ok, since the BBNS is during the first ~3...
  33. J

    Programs PhD in Cosmology = life in academia?

    I find myself very interested in Cosmology and would consider doing a PhD in the field, however I am not sure if I would like to be an academic or not. Given the relatively few technical applications of Cosmology, would it be wiser for me to enter a field with greater possibilities for...
  34. wolram

    Diminishing Results in Cosmology: Public Interest Fading?

    I think string theory and quantum loop theory are the instigators in destroying public interest in cosmology, pop articles promised so much ,but nothing emerged, i also think that funding of cosmology projects will decline with diminishing results, it is no fault of the scientist, just bad luck...
  35. marcus

    Penrose on YouTube, before bang cosmology, eight episodes October 2007

    Penrose has given this Before the Big Bang talk repeatedly over several years and it has developed. Some new thoughts, new cartoon drawings. Here on YouTube is a version he gave 31 October 2007 at George Mason University (Fairfax, Virginia, near Washington DC). It comes in several segments. The...
  36. D

    Alternative cosmology: the arp-narlikar's variable mass theory

    Hi! I'm interested in alternative cosmologies and the variable mass hypothesis developed by arp and narlikar seems to explain better the discordant redshifts: but I can't understand how this theory calculates cosmic distances according redshift and time. Narlikar says that " We have here a flat...
  37. Loren Booda

    Cosmology: Science of the Universe, by E. R. Harrison

    Have you read this book (2nd edition), and if so, what do you think of its approach to cosmology? Personally, it is one of my all-time favorite physics books - joyfully understandable, beautifully imaginative and lastingly philosophical.
  38. marcus

    Is the Big Bang No Longer the Beginning?

    It is conjectured that we are at an historic watershed when people will stop thinking of the big bang as the Beginning of time or our universe, but will see it as a step along the way. The frontiers of science---what we can model and test---are being pushed back to conditions prior to the onset...
  39. D

    Grad Level Cosmology Books: Structure Formation & More

    Hi there, I was wondering if anyone had any recommendation on a good grad level cosmology book. Something dealing with more astrophysical things like structure formation. I'm using the Cole & Lucchin book for my class now and am not really a big fan of it. The other books I've found are either...
  40. L

    Logical Positivism versus Cosmology

    When I went through a course on Relativity, the professor said that relativity was at its foundation based on the philosophy of logical positivism (i.e., the only meaningful discussion is of observations, no discussion of a larger reality is meaningful), which seems to preclude larger...
  41. G

    The End of Cosmology: Is Special Relativity at Odds?

    The other day I read a rencent article in Scientific American entitled "The End of Cosmology." I have a simple question that I hope someone can clarify for me. Let me first give a brief summary and my understanding of the article. In every direction the universe is expanding, and this...
  42. C

    Cosmology getting stale with discoveries?

    Greetings, I was an avid amateur cosmologist for a few years, but lost interest 2 years ago. What I recall is a few basics like: 1) Univ is ~13.7 billion years old 2) Univ is accelerating in expansion 3) WMAP measured ~2.75 Kelvin vacuum temp. 4) Space is indeed flat Euclidean...
  43. S

    Good textbooks on modern cosmology ?

    Is there a modern cosmology textbook as good or better than Scott Dodelson's?
  44. W

    Is cosmology an extension of creation science?

    Is cosmology an attempt of the church to highjack science? Is this cosmology the beginning of a new breed of "science" where belief is protected and taught under the name of science?
  45. D

    Solving Cosmology Question: Redshift where Radiation = Matter Energy Density

    Hi guys, I'm in a pickle here with an assignment. I'm required to find the redshift at which the energy density in radiation equals the energy density in matter. The following are the givens we were...well, given: 1) assume 1 baryon = 10^9 photon 2) assume all photons have energy to the...
  46. J

    Thermodynamics Versus Cosmology

    I don't know if this is the appropriate forum for my dilemma, but here it goes: Second law of thermodynamics says that the entropy in the universe increases. In every texbook I have learned, ice is considered to have low entropy. When it melts, entropy increases. When that water becomes water...
  47. C

    Seventh Alexander Friedmann International Seminar On Gravitation And Cosmology

    Here is the homepage of the event -- to be held from Jun 19 to Jul 05 2008, in João Pessoa, Brazil: http://www.fisica.ufpb.br/eventos/friedmann2008/friedmann2008new2.htm http://www.fisica.ufpb.br/eventos/friedmann2008/friedmann2008new2_arquivos/page0016.htm" are the current scheduled...
  48. M

    Cosmology Question: Expansion of the Universe

    Homework Statement So the other day in my cosmology class we talked about whether smaller objects like a solar system, a star or a galaxy expand with the rest of the universe. While the answer is obviously no, since local gravitational forces can overcome that expansion, our professor...
  49. D

    What is the difference between cosmology and astrophysics

    hi. this is probably in the wrong place, but what is the difference between cosmology and astrophysics... i only ask because i wanted to be an astrophysisist, but before i make up my mind for sure i just want to know what cosmology is... thankyou dan
  50. jal

    How Does Solid Hydrogen Impact Our Understanding of Cosmology?

    Here is what I have learned ,….. the experiments on “warm dense matter” (WDM) will have impact on Cosmology. Ionized might be a good word to describe the universe prior decoupling. There will be new calculations to try to understand the universe before decoupling (400,000 years) Prior to...
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